21407813 has 16 divisors (see below), whose sum is σ = 26248320. Its totient is φ = 17050176.

The previous prime is 21407809. The next prime is 21407821. The reversal of 21407813 is 31870412.

It is a cyclic number.

It is not a de Polignac number, because 21407813 - 2² = 21407809 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21407213) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5531 + ... + 8567.

It is an arithmetic number, because the mean of its divisors is an integer number (1640520).

Almost surely, 2^21407813 is an apocalyptic number.

It is an amenable number.

21407813 is a deficient number, since it is larger than the sum of its proper divisors (4840507).

21407813 is a wasteful number, since it uses less digits than its factorization.

21407813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3116.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21407813 is about 4626.8577890400. The cubic root of 21407813 is about 277.6668930876. Note that the first 3 decimals are identical.

The spelling of 21407813 in words is "twenty-one million, four hundred seven thousand, eight hundred thirteen".